Two aging crooks are given two weeks to repay a debt to a woman named The American. They recruit their recently deceased partner's son to help them break into a laboratory and steal the vaccine against STBO, a sexually transmitted disease that is sweeping the country. It's spread by having sex without emotional involvement, and most of its victims are teenagers who make love out of curiosity rather than commitment.

Paris by night. Alex, 22, wants to become a filmmaker. He is fascinated by first times and his girlfriend, Florence, has just left him for his best friend, Thomas. First break-up, first attempted murder: Alex tries to strangle Thomas, but gives up and wanders the streets. That evening, Mireille, a girl from provincial France who has come up to Paris to make commercials, is left by her boyfriend. Alex witnesses this separation. These two tormented souls run into each other at a party.